In digital systems, ripple counters are widely used for data recognition and bit data stream control, for example. Ripple counters used in most digital systems contain a number of D-type flip-flops (DFFs) to count clocks during a specific time interval. With the count of clocks, the digital system recognizes the number of bits that are inputted or outputted through the assigned pin. For example, U.S. Pat. No. 6,853,698 granted to Nguyen on Feb. 8, 2005 discloses a ripple counter circuit that includes series-connected DFFs for counting input clock pulses.
Conventional ripple counters have setup and hold times. In a case where the pulse widths of the input clocks are narrower than the critical time period specified by their setup and hold times, the ripple counters may function incorrectly.